allow zooming on desktop when holding ctrl and scrolling

add prototype of selection mode, span up dashed rectangle

lib/canvas/drawing_page.dart

@@ -2,6 +2,7 @@ import 'dart:ui';
 
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
 
 import '../context/file_change_notifier.dart';
@@ -151,9 +152,18 @@ class _DrawingPageState extends State<DrawingPage> {
         debugPrint('got pointer signal: $pointerSignal');
 
         if (pointerSignal is PointerScrollEvent) {
+          final bool ctrlPressed = RawKeyboard.instance.keysPressed
+              .contains(LogicalKeyboardKey.controlLeft);
+
           final delta = pointerSignal.scrollDelta;
+          if (ctrlPressed) {
+            setState(() {
+              zoom = (zoom - delta.dy.sign * .1).clamp(0.25, 5.0);
+            });
+          } else {
             _calcNewPageOffset(-delta, size.width);
           }
+        }
       },
       onPointerDown: (d) {
         Offset pos = d.localPosition;

lib/canvas/my_painter.dart

@@ -3,6 +3,8 @@ import 'dart:math';
 import 'package:flutter/material.dart';
 
 import 'paint_controller.dart';
+import 'path/path_transform.dart';
+import 'path/ring_number_provider.dart';
 import 'screen_document_mapping.dart';
 
 final Rect a4Page =
@@ -81,8 +83,9 @@ class MyPainter extends CustomPainter {
       }
     }
 
-    // active eraser outline
-    if (activePen == Pen.eraser) {
+    // active pen hover effects
+    switch (activePen) {
+      case Pen.eraser:
         final pointerpos = controller.getPointerPosition();
         if (pointerpos != null) {
           final translatedPointerpos = _translatept(pointerpos, size);
@@ -93,6 +96,24 @@ class MyPainter extends CustomPainter {
                 ..style = PaintingStyle.stroke
                 ..color = Colors.grey);
         }
+        break;
+      case Pen.selector:
+        final selection = controller.getSelection();
+        if (selection != null) {
+          final rectpath = (Path()
+                ..addRect(Rect.fromPoints(_translatept(selection.topLeft, size),
+                    _translatept(selection.bottomRight, size))))
+              .dashPath(RingNumberProvider([3, 5]));
+
+          canvas.drawPath(
+              rectpath,
+              paint
+                ..style = PaintingStyle.stroke
+                ..color = Colors.grey);
+        }
+        break;
+      default:
+        break;
     }
   }
 

lib/canvas/paint_controller.dart

@@ -18,6 +18,7 @@ class PaintController extends ChangeNotifier {
   Offset? _currentPointerPosition;
   Pen activePen = Pen.pen;
   List<Stroke> strokes = [];
+  Offset? _selectionStart;
 
   PaintController(this.file);
 
@@ -37,9 +38,9 @@ class PaintController extends ChangeNotifier {
       // todo line drawn on edge where line left page
       if (!a4Page.contains(offset)) return;
 
-      // todo handle other pens
-      if (activePen == Pen.eraser || activePen == Pen.selector) return;
-
+      switch (activePen) {
+        case Pen.pen:
+        case Pen.highlighter:
           int strokeid = strokes.isNotEmpty ? strokes.last.id + 1 : 0;
           final color = activePen == Pen.pen
               ? const Color(0xFF444444)
@@ -48,15 +49,28 @@ class PaintController extends ChangeNotifier {
               [Point(offset, _calcTiltedWidth(3.0, e.tilt))], strokeid, color));
           file.addStroke(strokeid, color);
           notifyListeners();
+          break;
+        case Pen.selector:
+          _selectionStart = offset;
+          break;
+        default:
+          break;
       }
     }
+  }
+
+  Rect? getSelection() {
+    if (_currentPointerPosition == null || _selectionStart == null) return null;
+    return Rect.fromPoints(_selectionStart!, _currentPointerPosition!);
+  }
 
   void pointUpEvent(PointerUpEvent e) {
     _currentPointerPosition = null;
     notifyListeners();
 
-    if (activePen == Pen.eraser) return;
-
+    switch (activePen) {
+      case Pen.pen:
+      case Pen.highlighter:
         // pointerupevent doesn't deliver correct event button
         if (_allowedToDraw(e.kind, 1)) {
           final lastStroke = strokes.last;
@@ -70,6 +84,14 @@ class PaintController extends ChangeNotifier {
             file.addPoints(lastStroke.id, lastStroke.points);
           }
         }
+        break;
+      case Pen.selector:
+        _selectionStart = null;
+        // todo highlight current selection
+        break;
+      default:
+        break;
+    }
   }
 
   void pointMoveEvent(Offset offset, PointerMoveEvent event) {

lib/canvas/path/path_transform.dart

@@ -0,0 +1,25 @@
+import 'dart:ui';
+
+import 'ring_number_provider.dart';
+
+extension DashPath on Path {
+  // creates a new dashed path with the given intervals
+  Path dashPath(RingNumberProvider dashArray) {
+    final Path dest = Path();
+    for (final PathMetric metric in computeMetrics()) {
+      double distance = .0;
+      bool draw = true;
+      while (distance < metric.length) {
+        final double len = dashArray.next;
+        if (draw) {
+          dest.addPath(
+              metric.extractPath(distance, distance + len), Offset.zero);
+        }
+        distance += len;
+        draw = !draw;
+      }
+    }
+
+    return dest;
+  }
+}

lib/canvas/path/ring_number_provider.dart

@@ -0,0 +1,13 @@
+class RingNumberProvider {
+  RingNumberProvider(this._vals);
+
+  final List<double> _vals;
+  int _idx = 0;
+
+  double get next {
+    if (_idx >= _vals.length) {
+      _idx = 0;
+    }
+    return _vals[_idx++];
+  }
+}